The invention relates to a digital transmission system having a transmitter and a receiver, the transmitter including a coder and the receiver including a decoder, for subband coding of a digital signal, such as a digital audio signal, having a given sampling rate F.sub.S. The coder is responsive to the digital signal, for generating a number of M sub-band signals with sampling rate reduction, and divides the digital signal band into successive subbands of band numbers m(1.ltoreq.m.ltoreq.M) increasing with frequency. The decoder is responsive to the M subband signals for constructing a replica of the digital signal, and merges the subbands to the digital signal band, with sampling rate increase. The invention also relates to a transmitter and a receiver for use in the transmission system, a coder for use in the transmitter, a decoder for use in the receiver, an analysis filter for use in the coder, a synthesis filter for use in the decoder, and a digital audio signal recording or reproducing apparatus comprising the transmitter and the receiver respectively.
A system for subband coding is known from the article entitled "The critical Band Coder-Digital encoding of speech signals based on the perceptual requirements of the auditory system" by M. E. Krasner, Proc. IEEE ICASSP80, Vol. 1, pp. 327-311, Apr. 9-11, 1980. In this known system, use is made of a subdivision of the speech signal band into a number of subbands, whose bandwidths approximately correspond with the bandwidth of the critical bands of the human auditory system in the respective frequency ranges (compare FIG. 2 in the article by Krasner). This subdivision has been chosen because on the basis of psycho acoustic experiments it may be expected that in a such like subband the quantization noise will be optimally masked by the signals within this subband when the quantizing takes account of the noise masking curve of the human auditory system (this curve indicates the threshold for masking the noise in a critical band by a single tone in the centre of the critical band, compare FIG. 3 in Krasner's article.